ASoC: Optimise WM8996 no interrupt path

This occurs frequently if we are in edge triggered mode as we must poll the
interrupt status register until we get no more interrupts so it's worth
the effort - it means we skip writing null acknowledgements to the chip.

Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>
Acked-by: Liam Girdwood <lrg@ti.com>

sound/soc/codecs/wm8996.c

@@ -2408,6 +2408,9 @@ static irqreturn_t wm8996_irq(int irq, void *data)
 	}
 	irq_val &= ~snd_soc_read(codec, WM8996_INTERRUPT_STATUS_2_MASK);
 
+	if (!irq_val)
+		return IRQ_NONE;
+
 	snd_soc_write(codec, WM8996_INTERRUPT_STATUS_2, irq_val);
 
 	if (irq_val & (WM8996_DCS_DONE_01_EINT | WM8996_DCS_DONE_23_EINT)) {
@@ -2426,10 +2429,7 @@ static irqreturn_t wm8996_irq(int irq, void *data)
 	if (irq_val & WM8996_MICD_EINT)
 		wm8996_micd(codec);
 
-	if (irq_val)
-		return IRQ_HANDLED;
-	else
-		return IRQ_NONE;
+	return IRQ_HANDLED;
 }
 
 static irqreturn_t wm8996_edge_irq(int irq, void *data)